Remote control system



April 6, 1948. H. G. EVERS REMOTE CONTROL SYSTEM 3 Sheets-Sheet 1- Filed Aug. 5, 1944 REGISTER RELAYS CONTROL DEVICE CONTROL DEVICE INVENTOR. HARRY G. E V ERS ATTORNEY A ril 6, 1948. H, G, EVERS. I 2,439,205

REMOTE CONTROL -SYS TEM Filed Aug. 5, 1944 3 Sheets-Sheet 2 ZHA) AUTOMATIC CODE SENDER F |G.2 EMA 213A, 224 2|2A) I Y I l l 223 262 v 241 228 1 am I l 5512a Li. '1

227. .260 I --r-J 25 r My RF 30s I 40m 305 OSCILLATOR CEIVER 306 I 303 A'F' MODULATOR OSCILLATOR RADIO LINK 302 INVENTOR.

HARRY G. EVERS ATTORNEY April 6,1948. H. e. EVERS REMOTE CONTROL SYSTEM Filed Aug. 3, 1944 5 Sheets-Sheet 3 R m H W.

HARRY G. EVERS ATTORNEY Patented Apr. 6, 1948 REMOTE CONTROL SYSTEM Harry G. Ev ers, Chicago, 111., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application August 3, 1944, SerialNo. 547,955

.2 Claims. (01. 177-353) The present invention pertains to remote control systems for selectively controlling a number of apparatus units at a remote point over a single control channel, and more particularly tosystems wherein the control is effected by coded operation by the operator and to provide for the release of either or both of the operated apparatus units by a further single operation.

Another object is to providefor selective operation of any one of the apparatus units for a predetermined time interval in response to a momentary operation of the corresponding control switch including strapping means for at times changing the length of the time interval.

A still further object is to provide a code transmitter and an associated register that will transmit codes in the same sequence in which the corresponding control circuits are closed even though they may both be closed before the code transmitter has started to transmit.

In the specific embodiment of the invention herein described the invention is used to control the flight of an airplane from a ground station .or from a second airplane by means of a radio link. The invention has been illustrated by schematic diagrams comprising Figs. 1 to 4, in which:

Fig. l is a schematic diagram of the control device and the associated register relays,

Fig. 1A illustrates the construction of the control device,

Fig. 2 shows the automatic code sender,

Fig. 3 is a block diagram of the radio link,

Fig. 4 shows the control relays which are located in the controlled plane.

The control device I illustrated in Fig. 1A comprises a shaft ass supported by and extending through a flexible rubber mounting I39 which normally holds the shaft 138 in a vertical, or neutral, position. One end of this shaft serves as a handle and the opposite end carries a cam iili. Four, snap-action switches N13 to Hitare mounted around the cam and are spaced apart. The flexible mounting permits movement of the cam from its neutral position so as to opcrate any one of the switches individually or so as to operate any two adjacent switches simultaneously. The handle of the control device simulates the control stick normally used to control the flight oi an airplane, the movement of the handle to operate any of the four switches corresponding to the movement of a control stick in an airplane to control the rudder and elevators.

The relay equipment shown at the right of the control device in Fig. 1 consists of two relay registers, each capable of storing one of two control signals and a release signal. One of these relay registers is associated with switches in the control device which are operated by upward or downward movement of the cam and the second relay register is associated with the remaining two switches which are operated by lateral movement of the cam. The purpose of these two relay registers is to determine what code the automatic code sender should transmit and in the case of aseries of codes to determine the sequence in which the series of codes are transmitted.

The automatic code sender and interval timer shown in Fig. 2 consists of a pair of pulse gen eratingrelays 2i]? and 208, a series of counting relays 2m to 2M, start relays 284 and 265, spacing relays 2i]! and 203, and several auxiliary relays. Whenever the start'relays are operated by the relay registers the pulse generating relays operate to generate impulses. The register relays also cause a particular one of the counting relays to operate. The impulses generated by the pulse generating relays cause the counting relays succeeding the particular counting relay ope erated by the register relays to be operated one at a time. When the last countingrelay operates it stops the operation of the pulse generating relays. The number of impulses generated thus depends on the particular counting relay operated by the relay registers. The impulses are transmitted to the controlled plane simultaneously with the operation of the counting relays. At the conclusion of each series of impulses the spacing relays cause the pulse generating relays and the counting relays to go through another cycle of operations without transmitting any impulses to the controlled plane. This spacing interval serves two purposes, first it provides time for the control relays in the controlled plane to reset themselves after a series of impulses so as to be prepared for a second series, and secondly it provides for the operation of an apparatus unit in the controlled plane for a definite time interval in response to only a momentary operation of the corresponding switch in the control device.

The radio link, which serves as the control channel in this particular application of the invention, has been shown in block form in Fig. 3 as the details of this equipment form no part of the invention. Fig. 3 indicates that the radio frequency oscillator 301 and the audio frequency oscillator 302 used to modulate the radio frequency carrier are both controlled by the auto matic code sender. This control may be effected by any of the numerous methods familiar to those versed in the art. Similarly any familiar method may be used for deriving a direct current from the audio signal in the receiver 303 of the controlled plane to operate a relay.

The control relay circuit shown in Fig. 4 comprises an impulsing relay 40I. lock pulse. relay 402, counting relays 406 to 410., pulse directing relay 403, slow release relays 404 and- 405, register relays 4H to 4 I4, and release relay 4| 5. When the automatic code sender at the control station operates it starts the radio frequency oscillator to. generate the carrier wave and causes the audio frequency oscillator to operate intermittently in accordance with the code to be transmitted. The carrier wave with the audio signalsuperimposed on it is transmitted to the controlled plane where the signal is demodulated and the audio component isv rectified to furnish a direct current to. the impulsing relay 401 of Fig. 4, which is thus. caused to repeat the impulses to the counting relays. One of the counting relays is operated for each impulse received. At the end of the'series of impulses a momentary circuit is completed, through contacts of the last counting relay operated, to the corresponding register relay or to the release relay. When a register relay is operated by this momentary circuit it locks itself operated under the control of the release relay and closes an operating circuit to its corresponding apparatus unit. The register relay remains operated until a release code is received, which may not occur until other register relays have been operated. Each of the register relays corresponds to one of the switches in the control device, the object being-to operate the register relays in accordance with the condition of the switches in the control device. Whenever any of the switches in thev control device is released the release relay in Fig. 4 is operated and it releases the register relays. If two switches in the control device have been operated and then only one is released the release relay in Fig. 4 will operate to release both of the corresponding register relays in the controlled plane but the automatic code sender at the controlling station will immediately cause the reoperation of the register relay in the controlled plane corresponding to the switch which remains operated.

The contacts of the register relays in Fig. 4 may be used as shown to control reversible electric motors M6 and 4H which are arranged to control the position of the rudder and elevators of the controlled plane through suitable gearing 4 and mechanical couplings. Limit switches may also be provided for these motors to restrict the motion of the rudder and elevators within any desired limits.

The operation will now be described in greater detail with reference to the accompanying drawings. The operation of Figs. 1 and 2 may be followed conveniently if they are placed side by side with Fig. l on the left. In Fig. 1 it will be seen that for each of the four switches I03 to I06 there is provided a corresponding register relay I09, H2, I08 and H3, and that a release relay H0 or H4. is provided for each pair of switches. The circuit to relay H0 is normally open at contacts of relays I01 to I09, and the circuit to relay H4 is likewise normally open at contacts of relays III to H3. Assuming that it is desired to cause the controlled plane to turn to the left, the operator moves the handle of the of relay I09 over an obvious circuit.

Relay I09 operates and closes its locking circuit through contacts H6 to contacts II1 of relay I01, closes a circuit to the start relay 205 over lead 205A at contacts H8, prepares a circuit to. relay H0 at contacts H9, prepares a circuit. to relay I01 from lead II5A at contacts I20, and prepares a circuit to counting relay 2I3 over lead 2I3A from lead 200 at contacts I23. Relay 205. operates, closes a circuit to relay 204 at contacts 2I6, prepares a locking circuit for the counting relays at contacts 2I1, closes a circuit at contacts 2I8 to connect leads 304 and 305 to start the radio frequency oscillator 30L and closes circuits to relays 2I3 and 206 at contacts 2I9. The circuit for relay 206 may be traced from battery at contacts 2 I9 through contacts 220 of relay 2I0, contacts 22I of relay 204, through relay 206 to ground at contacts 222 of relay 208. The circuit for relay 2I3 may be traced from battery at contacts 2I9 through contacts. 223 of relay 20I, lead 200, contacts I2I of relay H3, contacts I22 of relay I08, contacts I23 of relay I09, lead 2I3A, contacts 224 of relay 2I4 to relay 2I3. Relay 206 operates, closes its locking circuit at contacts 225, and connects leads 306 and 301 at contacts 226 to start the audio frequency oscillator 302. Relay 2I3 operates, closes its locking circuit at contacts 221 to contacts 2I1 of relay 205, and prepares a circuit to the succeeding counting relay 2I2 at contacts 228. Relay 204 operates, opens the operating circuit for relay 206 and closes a circuit to relay 208 at contacts 22 I, closes a second locking circuit for relay I09 over lead I08A at contacts 229, prepares locking circuits for relays 202 and 2I5 at contacts 230, and prepares a circuit for relay I01 over lead II5A at contacts 23I.

Relay 208 operatesv and closes a circuit to relay 201 at contacts 23L Relay 20:1 operates and opens the circuit to relay 208 at contacts 232. Relay 208 restores and opens the circuit to relay 201 which restores. and re-closes the circuit to relay 208. This cycle of operations continues as long as battery is available from contacts 2I9 of relay 205 to operate relay 2108. The release times of relays 201 and 208 can be adjusted by means of adjustable shunting resistors 233 and 234, respectively, to secure the desired speed of operation and optimum per cent closure time of the contacts. of relay 208. The first operation of relay 208 opens the circuit to relay 206 at contacts 222, closes. a multiple circuit toleads 306 and 301 at contacts 263., and closes a circuit to relay 2I2 and 301 at contacts 253 to interrupt the operation of the audio frequency oscillator 302, opens the operating circuit to relay 2I2 and closes an obvious circuit to relay 209 at contacts 235. Pulse directing relay 209 operates, prepares a circuit for relay 2! I at contacts 236 through contacts 231 of relay M2, and closes its own locking circuit at contacts 239. The second operation of relay 208 closes a multiple circuit to relay 209 at contacts 222, closes a circuit to relay 2H at contacts 235, and re-closes the circuit between leads 305 and 301 at contacts 253. Relay 2 operates, closes its locking circuit at contacts 240, prepares a circuit to relay 2I0' at contacts MI, and opens the operating circuit to relay 200 at contacts 242. The second restoration of relay 208 opens the circuit to relay 209 at contacts 222, opens the operating circuit to relay 2! I at contacts 235, and again interrupts the operation of the audio frequency oscillator at contacts 253. Relay 200 restores and prepares a circuit to relay 2I0 through contacts 24 of relay 2| I. The third operation of relay 202 closes the circuit to relay 2 I at contacts 235 and closes the circuit to the audio frequency oscillator 302 atcontacts 253 for the third time. Relay 2Iil operates, closes its locking circuit at contacts 243, prepares a circuit to relay 202 at contacts 244, and opens a second point in the circuit to relay 2% at contacts 220 to prevent any further cycling of relays201 and 208. When relay 203 restores for the third time it closes a circuit to relay 202 at contacts 235 through contacts 244 of relay 'ZIll, and opens the circuit to the audio frequency oscillator 302 at contacts 263. Relay 202 operates, opens the circuit to relay 205 at contacts 245, closes its locking circuit at contacts 246, and prepares a circuit for relay I01 over lead II A at contacts 241. Relay 205 restores, opens the circuit to the radio frequency oscillator 30! at contacts 2 I0, opens the circuit to relay 204 at contacts 2I5, opens the locking circuit to the counting relays at contacts 2 I I, and closes a circuit to relay I01 at contacts 243. This last circuit may be traced from contacts 248 through contacts 241 of relay 202, contacts 2 3I of relay 200, contacts 240 of relay 20!, contacts 250 of relay 203, contacts 25I of relay 2I5. lead II5A, contacts I20 of relay I09 to relay I01. Counting relays 2I0, 2II, H2, and 2I3 restore. Relay I 01 operates, opens the operating circuit for relay I09 at contacts I24, opens the first locking circuit for relay I09 at contacts II1, prepares a second circuit path to relay Ill! at contacts I 25, and closes its locking circuit at contacts I25 to contacts I 21 of relay I I5. Relay 204 restores, opens the second locking circuit for relay I09 over lead I08A at contacts 220, opens the locking circuit for relay 202 at contacts 230, opens the operating circuit to relay Isl over lead II5A and closes the circuit to relay 20I at contacts 23 I. The last circuit may be traced from contacts 208 of relay 235, through contacts 241 of relay 202, contacts 23! of relay 204, contacts 252 of relay 203 to relay 20!. Relay I00 restores and prepares a circuit to relay H5 from lead II 5A. Relay 20! operates, opens themarking lead 200 to the register relays of Fig. 1 and prepares a cir cuit to relay 2I3 at contacts 223, prepares a circuit to relay 205 at contacts 253, prepares a circuit to relay 203 at contacts 249, closes its looking I circuit at contacts 254 to contacts 255 of relay 203,

tacts 02! of relay 409.

and opens points in the circuits between leads 306 and i301 and between leads 304 and 305 at contacts 255 and 251 respectively, to prevent operation of the radio equipment during the spacing interval. Relay 202 restores, opens the operating circuit to relay 2M at contacts 241, and closes a circuit to relay 205 at contacts 245 through contacts 253 of relay 2!".

Relays205, 20 3,2I3, 225, 222, 201, 2I2, 2I I, 2I0, and 209 operate in the same manner as previously described except that the operating circuit to relay 2I3 is now through contacts 223 of relay 20I instead of through contacts of the relays in Fig. l. The operation of relay 202 and subsequent release of relay 205 after this second cycle of operations closes a circuit to relay 203 from contacts 2% of relay 205, through contacts 241 of relay 202, contacts 23! of relay 2%, and contacts 249 of relay 20I. Relay 203 operates, closes its locking circuit at contacts 250, and opens the locking circuit to relay 20! at contacts 255. Relay 20I restores and opens the operating circuit to relay 203 at contacts 249. Relay 20 i restores and opens the locking circuit to relay 202 at contacts 230. Relay 262 restores and opens the locking circuit to relay 203 at contacts 241; Relay 203 restores. All relays are now released except relay I01 which remains locked to contactsIZl of relay H5.

The operation of the radio link and the control relays shown in Fig. 4 will now be described. It will be recalled that during the operation of the automatic code sender of Fig. 2 that leads 304 and 305 were connected during the first cycle of operations and that during this same cycle of operations leads 3% and 301 were closed three tirnes during successive operations of relay 208. The closure of leads 324 and 305 caused the radio transmitter of Fig. 3 to produce a high frequency carrier which is radiated by aerial 308 and received through antenna 300 of the receiver 303 in the controlled plane. The reception of this carrier does not produce any output on lead 40IA as yet. However, each time that leads 305 and 301 are closed the audio frequency oscillator 302 produces an audio signal which is used to modulate the high irequency carrier. The receiver 303 demodulates the modulated carrier to reproduce the audio signal. A direct voltage is then derived from the audio signal and is used to operate a sensitive relay which is included in the receiver. Contacts on this sensitive relay are used to close a circuit between leads AMA and battery. By this means pulses of direct current are applied to lead 40M corresponding to the operations of relay 2&3 of the automatic code sender.

Referring now to Fig. 4., each pulse of current over lead itIA causes relay 40! to operate. On the first pulse relay dtI operates, closes its looking circuit at contacts M5, closes a circuit to relay 404 at contacts 451, and closes a circuit to relay M0 at contacts 0-!3 through contacts MB of relay 403, contacts 420 of relay 401, and con A circuit to lock'pulse relay 432 is also closed at contacts are of relay 40L By properly proportioning the resistance and number of turns used in the coil winding of relay 002 it can he made slower to operate than any of the counting relays 406 to 4| 0, thus incuring that relay 45H will remain looked through contacts 022 of relay W2 until the counting relay has operated when the pulse of current on lead MIA is of short duration. Relay 4I0 operates, prepares its locking circuit at contacts 423, prepares a circuit to, relay 400- at contacts 424', and prepares a circuit to relay 403 at contacts 425. Relay 402 operates, opens the locking circuit to relay 40I and closes a multiple circuit to relay 404 at contacts 422. Relay 404 operates, prepares a bleeder circuit to itself through resistor 432 at contacts 420, closes a circuit to relay 405 at contacts 421, and closes a locking circuit for the counting relays at contacts 420. It should be noted here that the first impulse in each series produced by the automatic code sender is longer than the remaining impulse in order to insure that relay 404 has sufficient time to operate and prepare the locking circuit for the counting relays. Relay 405 operates and closes a multiple circuit for locking the counting relays at contacts 429. At the end of the first pulse of direct current on lead 40IA the circuit to relay 40I is opened. Relay 40I restores, 'opens the operating circuit to relay 404 at contacts 4Il, opens the operating circuits to relays 402 and 4! at contacts 4I8, and

closes a circuit to relay 403 at contacts 4 I 8 through contacts 430 of relay 409 and contacts 425 of relay 4I0. The circuit to relay 402 is maintained through contacts 4!!) of relay 403 contacts 420 of relay 401, contacts 42I of relay 409, contacts 423 of relay 4I0, and contacts 428 of relay 404. Relay 403 operates, closes its locking circuit at contacts 43!, and opens the holding circuit for relay 402 and prepares a circuit to relay 409 at contacts 419. Relay 402 restores, opens the holding ircuit to relay 404, and prepares the locking circuit to relay 40L The circuit to relay 404 is now completed through contacts 423 and resistor 432. Re-

sistor 432 is high enough so that relay 404 cannot remain operated in series with this resistance incontacts 433 of relay 408, and contacts 424 of relay M0, and closes a holding circuit to relay 403 at contacts 434. Relay 409 operates, closes its locking circuit at contacts 435, prepares a circuit to relay 408 at contacts 42I', and opens the operating circuit to relay 403 at contacts 4-30. Relay 402 operates, opens the locking circuit to relay 40I and closes a multiple circuit to relay 404 at contacts 422. Relay 40I restores either when its locking circuit is opened orwhen the pulse of current on lead 40I A ceases, depending on which event occurs last. When it restores it opens the holding circuit for relay 403 at contacts 434.

Relay 403 restores, opens the holding circuit for relay 402 and prepares a circuit for relay 408 at contacts 4I0. Relay 402 restores. The third pulse of current over lead 40IA operates relay 40I for the third time causing the operation of relays 408 and 402. The operation of relay 408 prepares a circuit to relay 403 at contacts 436 which is completed at contacts MB of relay 40.I when it restores for the third time. then operates and opens the holding circuit to relay 402 at contacts 4 I 9 which releases and opens the' holding circuit to relay 404 at contacts 422. At this time relays 403, 404, 405, 408, 409, and M are operated. Relay 404 restores, opens the circuit to relay 405 and closes a circuit to relay M3 at contacts 421 through contacts 431 of relay 405, contacts 438 of relay 406, contacts 439 of relay Relay 403 l 401', and contacts 440 of relay 408. Relay 4I-3 operates, closes its locking circuit at contacts 441, prepares a locking circuit for relay M5 at con tacts 442, and closes a circuit to motor 4I5 at contacts 443. Relay 405 restores, opens the operating circuit to relay M3 at contacts 431 and opens the locking circuit for the counting relays at contacts 429. Counting relays 408, 400, and 4m restore opening the circuit to relay 403 at contacts 430 causing it to restore.

All of the control relays are now normal with the exception of relay 4I3. The motor 4I0 operates -to turn the rudder of the controlled plane so as to direct the plane to the left. The motor will continue to operate until the rudder reaches the limit of its travel as determined by the location of the corresponding limit switch with respect to the rudder.

The motor may be stopped at any intermediate point by restoring the cam IOI of the con trol device I00 to neutral. This operation brings about the release of relay 4I3 as will presently be described. The arc through which the rudder moves is thus determined by the length of time that the control device I00 is held in the operated position. Since it is difficult for an operator to estimate short time intervals the automatic code sender is arranged to provide a predetermined minimum time interval between operation and release signals so that the rudder can be moved through a small arc in response to only a momentary operation of the control device I00. This minimum time interval is introduced by the second cycle of operations of the pulse generating and counting relays of the code sender that was previously described' The duration of this time interval is determined by which one of the leads 2IIA to 2I4A that the make contact of contacts 223 is connected to as indicated by the dotted lines in Fig. 2.

The operation which brings about the release of relay 4 I3 and thus stops the operation of motor M6 in the event that the rudder has not yet reached the limit of its travel will now be described. It will be remembered from the previous description that all of the equipment in Figs. 1 and 2 is at normal except switch I03 and relay I01. When the control device is restored to the neutral position a circuit isclosed to relay H0 at switch I03 through switch I05 and contacts I25 of relay I01. Relay H0 operates, closes its lockingcircuit at contacts I28, closes a circuit to relay 205 over lead 205A at contacts I20, and prepares a circuit to relay ZI I over lead 2 I IA from lead 200. Relays 204 to 208 operate the same as previously described except that the operation of relay 205 closes a circuit to relay 2 at contacts 2!!) instead of to relay 2 I3 causing the operation of relay 2. This circuit may be traced from contacts 2I0 through contacts 223 of relay 20I, lead 200, contacts IZI of relay H3, contacts I22 of relay I08, contacts I23 of relay I09, contacts I30 of relay I42, contacts I3I of relay H0, and over lead 2| IA to relay 2| I. Thus'the first operation of relay 200 brings about the operation of counting relay 250 which prevents any further operation of relay 208 and thus permits only a single pulse of audio frequency modulation on the radio frequency carrier produced by the oscillator 30!. When relay 205 restores following the operation of relay 202, as previously described, a circuit is closed to relay H5 at contacts 248 of relay 205 through contacts 241 of relay 20,2, contacts 23I of relay 204, contacts 249 of relay 201, contacts 250 of relay 203, contacts 25I of relay 2I5, lead II5A, contacts I20 of relay I09, contacts I32 of relay I08, contacts I33 of relay H2, and

contacts I34 of relay H3. Relay H5 operates,

closes its locking circuit at contacts I35 to lead H53, opens the locking circuit to relay H at contacts Hit, and opens the locking circuit to relay I01 at contacts I21. Relay I01 restores and opens the operating circuit to relay H0 at contacts I25 causing it to restore. Relay 204 restores, closes a circuit to relay 20I causing it to operate and opens the locking circuit to relay 2'32. Relay 202 restores, closes a circuit to relay 205, and opens the locking circuit to relay H at contacts 241. Relay H5 restores completing the restoration of Fig. 1 to normal. Relay 205 operates and causes the automatic code sender to go through a second cycle of operations to produce a spacing interval in precisely the same manner previously described. The single audio frequency pulse applied to the carrier by the operation of the automatic code sender causes a single pulse of direct current to be received over lead 40IA of Fig. 4 to operate relay 40L Relays 40I, 402, 434, 435, and 4H) again operate as previously described. At the end of the pulse of current over lead 4% ill relay 40I restores and closes a circuit to relay liiti at contacts 4I8 through contacts 430 of relay 4% and contacts 425 of relay 4I0. Relay 403 operates and opens the holding circuit to relay 4t2 at contacts 4! 9 which restores and opens the holding circuit to relay 404 at contacts 422. Relay 404 restores, opens the circuit to relay 405 and closes a circuit to release relay M5 at contacts 421 through contacts 438 of relay 406, contacts 439 of relay 401, contacts 440 of relay 433, contacts 444 of relay 409, and contacts 445 of relay 4w. Relay 4I5 operates, closes its looking circuit at contacts 445, and opens the locking circuit to register relay 4l 3 at'contacts 441. Relay 4I3 restores, opens the locking circuit to relay 4 I 5 at contacts 442, and opens the circuit to motor M5 at contacts 443, if this circuit has not yet been opened by the limit switch. Relay 405 restores, opens the operating circuit to relay M5 at contacts 431, and opens the locking circuit to relay4l0 at contacts 429. Relay 4I5 restores. Relay 4I0 restores and opens the circuit to relay 403 at contacts 425 causing it to restore. All relays in the system are now at normal.

It will now be apparent that if the control device was operated so as to cause a momentary operation of switch M3 the operation would still be exactly the same except that relay H0 would be operated early in the cycle andwould cause the automatic code sender to send the release code, consisting of a single impulse, immediately after the spacing interval. The motor 4I6 would then be operated for a length of time equal to the spacing interval. Such a momentary operation of the control device may be repeated as often as desired to cause movement of the rudder of the controlled plane in discrete steps.

When the control device I40 is operated so as to cause cam it! to operate switch I05 the operation is similar to that described for the oper-- ation of switch I53 except that relay I08 is operated in place of relay I I39 and it causes counting relay 2I2 to be operated in place of relay 2I3 when relay 205 operates. As a result the first operation of relay 208 operates relay 2 and the second operation operates relay 2l0 to stop further impulsing. Two pulses of audio frequency modulation are thus applied to the carrier to cause two operations of relay 40| in the controlled planer These two operations of relay 40I causes counting relays M0 and 409 to be operated so that when relay 404 restores a circuit is completed to register relay '4I4 through contacts 444 of relay 499. The operation of relay 4I4 completes a circuit to motor 4I6 through a separate field winding causing it to run in the reverse direction to move the rudder so as to direct the controlled plane to the right. The release of relay 4 i4 is brought about by the operation of relay 455 the same as previously described when the control device I00 is returned to neutral.

In a similar manner the operation of the control device to the up or down positions causes the automatic code sender to delivera series of four or five impulses to the audio frequency oscillator 302 in response to the operation of switches I64 or I65 respectively. The operation of relays III to H4 which are associated with these switchesis the same as that of relays I01 to H0 except that a different one of the counting relays in the code sender is made to operate first. When relay H2 is operated a circuit is prepared through contacts 43a and lead 2I4A to operate relay 2I4 as soon as relay 2635 operates. An impulse is thus produced for each of the remaining counting relays 2!!! to 2I3. When relay H3 is operated none ofthe counting relays is operated by the operation of relay 295 and consequently five impulses will be produced by the automatic code sender. The first impulse will operate relay 2I4 and the fifth impulsewill operate relay 2l0. In either case relay 2I4 will be operated and will close a circuit to relay 2I5 at contacts 253. Relay 2G5 upon operating prepares a circuitto operate relay 253 on the succeeding operation of relay 208 at contacts 259, closes its locking circuit at contacts 25L and prepares a circuit to operate relay III over lead IIIA at contacts 25I at the end of the series of impulses. When four impulses are transmitted relay 4ii1 will be the last counting relay operated in Fig. 4 and will cause a circuit to be closed to register relay 4I2 through contacts 439 upon the release of relay 454 at the end of the series. If five impulses are transmitted relay 4% will also be operated causing the release of relay 404 to close a circuit to register relay 4! I. Relay 406 performs an extra function by opening the holding circuits for relays 43!! and 454 at contacts 448. This is a precaution to prevent a lock-up from occurring if more than five impulses are delivered to relay set through a false operation. The operation of relays 4H and M2 controls the operation of motor 4 to move the elevators of the controlled plane in the same manner as described for motor M6 in connection with the rudder.

Simultaneous operation of relays M I and 4 I 2 or of relays 4I3 and 4E4 is prevented by the relay registers associated with the control device. For example, if cam lei is moved so as to operate switch I and then is immediately moved to operate switch Id3 both relays I t5 and I09 will be operated. Relay H0 will also become operated during the time that the cam is being shifted from switch N15 to switch I03. In this case a code consisting of two impulses will first be transmitted to operate relay M4. The operation of relay I01 and the release of relay 284 at the end of the first cycle of operations of the automatic code sender will release bothrelays I08 and IE9. Relay H0 remains locked to contacts I36 of relay H5 and causes the code sender to send a release code consisting of one impulse which causes the release of relay M4. The operation of relay H5 at the end of this cycle of operations of the code sender releases relays I01 and H3. The release of relay I01 recloses the circuit to relay I09 from switch I03 allowing it to reoperate and cause the code sender to transmit a code consisting of three impulses to bring about the operation of relay M3. Although this sequence of operations takes a considerable time to describe it actually occurs in a very brief interval inasmuch as it has been found entirely practical t operate the equipment at a speed of thirty-five impulses per second and the longest single code which need be transmitted consists of five impulses.

The relay registers of Fig. 1 also control the sequence in which codes are transmitted when ,the control device is operated so as to actuate two adjacent switches simultaneously. This occurs when it is desired to cause the controlled plane to climb or dive and to turn at the same time. If it is desired that the controlled plane climb and turn left at the same time the control device I is operated so that cam IOI is moved to operate switches I03 and I04. Relays I09 and H2 will both be operated. The code for a left turn will be sent first due to marking of'the counting relays by contacts I23 of relay I09. Re-

lay I0I will be operated after this code has been transmitted and relay I09 will be released when its locking circuit over lead I08A is opened by the release of relay 204. After the spacing interval has been timed by the code sender the code corresponding to a climb will be transmitted due to the marking of the counting relays by contacts I30 of relay II2. At the end of this second code relay III will be operated and relay H2 will be released. The transmission of this second code brings about the operation of relay 4I2. Both motors M6 and 4H will now be operating simultaneously. If the control device is returned to release relays I I0 and I I4 will be operated and will cause the code sender to send the release code to operate relay 4| 5, thus releasing relays 4 I 2 and M3 to stop both motors. However, if it is desired to stop only one motor the control device may be operated to move cam IIlI from the position where both switches I03 and I04 are operated to a position where only one of the switches is operated without releasing the switch which remains operated. For example, in the above case the cam can be moved so that switch l03remains operated but switch I04 is released. Relay I I4 will then be operated through switches I06 and I04 and through contacts I31 of relay I I4. The operation of relay II I causes the code sender to transmit a release code which will bring about the operation of relay 4H) and consequent release of relays M2 and 4I3. Relay H will be operated after this code is sent and will cause the release of relays I01, III, and H4. The release of relay I01 re-closes the circuit to relay I09 from switch I03 which causes the code sender to retransmit the code for a left turn and thus causes the immediate re-operation of relay M3. The operation of motor M6 is thus only momentarily interrupted and the operation or motor 4" is stopped completely.

In the preceding paragraph it was assumed that switches I03 and I04 were operated simultaneously. This would cause the coded signal for a left turn to be transmitted first due to the preference given to this code in the marking chain. The sequence can be reversed by causing switch I04 to be operated slightly ahead of switch 12 I03. This will-permit relays H2 and 205 to become operated and thus cause the operation of relay 2I4 before relay I09 operates to interrupt the operating circuit for relay 2I4 at contacts I23. The operation oci relay I09 at this time will not alter the operation of the counting relaysbecause the marking circuit extending from lead 200 through contacts I23 of relay I09 to lead 2I3A is opened at contacts 224 of relay 2I4. Contacts 262 serve a similar purpose when relay I08 is operated during the time that the code sender is transmitting an up or down signal. Ihe code signals are thus transmitted in the same sequence that the control switches are operated in.

It will also be apparent from the preceding description that the cam IOI can be moved to operate one of the switches, say I04, to bring about the operation of the corresponding register relay 4I2, in the controlled plane and may then be moved so as to operate one of the adjacent switches, say I03, without releasing the first switch operated. This will cause the operation of the corresponding register relay, 4l3, without releasing relay 4I2.

While the invention has been described in connection with a radio link it is obvious that it may be used without such a link in other applications. If the radio link is omitted lead 306 of Fig. 2 is connected to lead 40IA of Fig. 4 and lead 301 is connected to battery of Fig. 4. Leads 304 and 305 are not required for this mode of operation.

Having described and illustrated the invention what is considered new and is desired to secure by Letters Patent is pointed out in the subjoined claims.

What is claimed is:

1. In a remote control system, a control station having a plurality of control switches and a code sender comprising a relay counting chain and impulsing means therefor, a remote station having a plurality of apparatus units each corresponding to one of said control switches, a signal channel therebetween, means at said control station'for operating said relay counting chain and impulsing means to transmit two coded signals over said signal channel in response to the operation of two of said control switches, means at said remote station for operating the corresponding apparatus units in response to the reception of said coded signals, and circuit arrangements causing said means at the control station to be operated in response to the release of one of said operated control switches to cause the relay counting chain and impulsing means to transmit a third coded signal to release the operated units 7 and to re-transmit one of said first two coded signals to reoperate the unit corresponding to the control switch remaining operated.

2. In a remote control system, a control station having a plurality of control switches and a code sender, a remote station having a plurality of apparatus units each corresponding to one of said control switches, a signal channel between said stations, means at said control station operated in response to the momentary operation of one of said control switches causing said code sender to transmit two coded signals over said signalling channel with a predetermined time interval between them, means at said remote station operated inresponse to the'reception of said coded signals causing the operation of the corresponding. apparatus unit for said predetermined time interval, and cross-connecting means for varying 13 the operation or said first means for changing the duration of said time interval.

HARRY G. EVERS.

REFERENCES CITED 5 The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Molina. Oct. 1, 1912 Herink Apr. 30, 1918 Chauveau Nov. 23, 1926 Beach Apr. 16, 1929 Number Number 

